Per Mertesacker and Laurent Koscielny are out for an unspecified amount of time says Wenger.(Getty Images)

Arsenal manager Arsene Wenger is uncertain how long defenders Per Mertesacker and Laurent Koscielny will be absent after the pair missed the Premier League draw with Liverpool at the Emirates Stadium. Mertesacker was ill for the clash while Koscielny watched the 0-0 stalemate from the stands after picking up a back problem.

Calum Chambers and Gabriel Paulista replaced the duo at the 11th hour and produced an uncertain performance on their way to keeping a clean sheet, as Philippe Coutinho twice struck the woodwork and Petr Cech saved well from a Christian Benteke effort. The showing exposed the importance of the Gunners' first choice defensive pairing but Wenger is not sure when they will be fit to return.

Newcastle United host Arsenal in their next league game on 29 August, before a home match against Stoke City is followed by a trip to champions Chelsea on 19 September. Wenger is not sure whether both players will be available for the upcoming matches having yet to ascertain the prognosis of the duo.

"Mertesacker is sick," Wenger said in his post-match press conference, according to the Arsenal's official website. "How long will that sickness take? I don't know. Koscielny has a back problem. Having said that, our two centre backs played well in the second half.

"Chambers and Gabriel do not have the experience of playing together, they've come in from one day into the next, but overall we didn't concede. Petr Cech saved us two or three times in the first half. In the second half I think we should've won the game. We were a bit unlucky, we lacked a bit physically and collectively to finish what we started.

"Our game is still not fluent enough in the final third, and that's why we didn't score. The West Ham game left a trace in our heads, and it was important tonight not to lose because you could see that was a shock for us and it was important for us to get that game out of our system."

Wenger has confirmed that Arsenal striker Danny Welbeck, who has missed four months with a knee problem, will not play in England's European Championship double-header against San Marino and Switzerland in early September. The 24 year old last saw action in the draw with Chelsea on 26 April but Wenger expects that he may return after the break. "After the international break, if all goes well, he can come back," the Frenchman posited.